Semiconductor processing methods

ABSTRACT

Some embodiments include methods in which insulative material is simultaneously deposited across both a front side of a semiconductor substrate, and across a back side of the substrate. Subsequently, openings may be etched through the insulative material across the front side, and the substrate may then be dipped within a plating bath to grow conductive contact regions within the openings. The insulative material across the back side may protect the back side from being plated during the growth of the conductive contact regions over the front side. In some embodiments, plasma-enhanced atomic layer deposition may be utilized for the deposition, and may be conducted at a temperature suitable to anneal passivation materials so that such annealing occurs simultaneously with the plasma-enhanced atomic layer deposition.

RELATED PATENT DATA

This patent resulted from a continuation of U.S. patent application Ser.No. 12/721,398, which was filed Mar. 10, 2010, and which is herebyincorporated herein by reference; which resulted from a continuation ofU.S. patent application Ser. No. 12/101,332, which was filed Apr. 11,2008, which issued as U.S. Pat. No. 7,704,884, and which is herebyincorporated herein by reference.

TECHNICAL FIELD

Semiconductor processing methods, methods of forming conductive contactregions for semiconductor wafer substrates, and methods of protecting asemiconductor wafer back side during plating of materials on thesemiconductor wafer front side.

BACKGROUND

Semiconductor constructions may comprise integrated circuitry supportedby a semiconductor wafer (such as, for example, a monocrystallinesilicon wafer). The integrated circuitry may include logic and/or one ormore memory arrays (such as, for example, dynamic random access memory(DRAM), and/or NAND memory).

The semiconductor constructions may also comprise electricallyconductive layers utilized to connect components of the integratedcircuitry with bond pad regions. Such electrically conductive layers maybe referred to as redistribution layers, in that they redistributeelectrical connections from one portion of a semiconductor constructionto another. Alternatively, such electrically conductive layers may bereferred to as bond pad supporting layers.

The bond pad regions may comprise one or more electrically conductivelayers formed over the bond pad supporting layers, and may be suitablefor connection to wire bonds, solder, or other materials utilized forelectrical connection to circuitry external of the semiconductorconstruction.

Difficulties may be encountered during formation of the bond padregions. Specifically, the bond pad regions may be plated onto the bondpad supporting layers by dipping the semiconductor construction within aplating bath. The semiconductor construction will have a front sidecomprising the bond pad supporting layers, and will have a back side inopposing relation to the front side. If plating occurs on the back side,such can waste plating components, and such may also form electricallyconductive structures which compromise performance of the integratedcircuitry associated with the wafer.

One method of addressing such difficulties is to form an electricallyinsulative layer across the back side prior to dipping the semiconductorconstruction within a plating bath. However, formation of theelectrically insulative layer comprises flipping the semiconductorconstruction so that the back side surface is up, followed by chemicalvapor deposition (CVD) of insulative material on the back side surface.The semiconductor construction is then flipped back over so that thefront side surface is up for subsequent processing. The flipping of thesemiconductor construction can cause abrasions or other defects. It isdesired to develop methods which avoid plating on the back side surfaceof a semiconductor construction, and yet which also avoid theproblematic flipping of the semiconductor construction.

Another aspect of the prior art is that there will often be one or morepassivation layers formed over the bond pad supporting layers. Suchpassivation layers may include a silicon nitride-containing layer. It isoften desired to anneal the silicon nitride-containing passivation layerat a temperature sufficiently high to promote hydrogen migration fromthe passivation layer, and/or otherwise thermally treat the passivationlayer. Such temperature may be at least about 400° C.

The anneal adds an additional process step. As each additional processstep reduces throughput, creates risk of error, and increases cost; itis desired to reduce the number of process steps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional view of a fragment of asemiconductor construction at a processing stage of an embodiment.

FIG. 2 is a diagrammatic three-dimensional view of the semiconductorconstruction comprising the fragment of FIG. 1; with the cross-sectionof FIG. 1 being along the line 1-1 of FIG. 2.

FIG. 3 shows the fragment of FIG. 1 at a processing stage subsequent tothat of FIG. 1.

FIG. 4 shows the fragment of FIG. 1 at a processing stage subsequent tothat of FIG. 3.

FIG. 5 shows the fragment of FIG. 1 at a processing stage subsequent tothat of FIG. 4.

FIG. 6 shows the fragment of FIG. 1 at a processing stage subsequent tothat of FIG. 5.

FIG. 7 shows the fragment of FIG. 1 at a processing stage subsequent tothat of FIG. 6.

FIG. 8 is a diagrammatic cross-sectional view of an apparatus that maybe utilized during the processing stage of FIG. 3.

FIG. 9 is a diagrammatic cross-sectional view of an apparatus that maybe utilized during the processing stage of FIG. 6.

FIG. 10 shows a fragment of a semiconductor construction in accordancewith an embodiment alternative to that of FIG. 3.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In some embodiments, insulative material (for instance, silicon nitride)is simultaneously deposited across both the front side and the back sideof a semiconductor wafer substrate. The deposition may be accomplishedutilizing any suitable method, such as, for example, plasma-enhancedatomic layer deposition (PEALD). The simultaneous deposition across thefront side and back side may form a protective layer across the backside without the prior art flipping of the semiconductor wafersubstrate. Further, the deposition may be conducted at a suitabletemperature so that thermal treatment of passivation materials occursduring the deposition, which may consolidate process steps and therebyimprove throughput and reduce costs. Another advantage may be thatpassivation film thickness can be reduced due to elimination ofpassivation film cracking, which may further reduce costs. Themethodology may be utilized with any of numerous semiconductorconstructions, including, for example, constructions comprising logic,DRAM arrays and/or NAND memory arrays.

Example embodiments are described with reference to FIGS. 1-10.

Referring to FIG. 1, such illustrates a fragment of a semiconductorconstruction 10. The semiconductor construction includes a bulksemiconductor base 12. Base 12 may comprise any suitable semiconductorcomposition, and may, for example, comprise, consist essentially of, orconsist of monocrystalline silicon. In some embodiments, base 12 maycorrespond to monocrystalline silicon lightly background doped withp-type dopant. The monocrystalline silicon may be in the form of awafer. The base 12, alone or in combination with other materials, may bereferred to as a semiconductor substrate. The terms “semiconductivesubstrate” and “semiconductor substrate” are defined to mean anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above.

In the shown embodiment, semiconductor base 12 supports levels 14, 16,18 and 20 of integrated circuitry. Although four levels are shown, inother embodiments there may be less than four levels or more than fourlevels. The levels of integrated circuitry are shown as blocks separatedfrom one another by interfaces diagrammatically illustrated by dashedlines. The levels may include any of numerous semiconductor componentsand insulative materials isolating the components from one another.Further, one or more of the levels may extend into base 12. In someembodiments, one or more of the levels may comprise logic, DRAM and/orNAND memory. If the levels comprise DRAM, such may include transistorsin combination with charge storage devices (for instance, capacitors);and if the levels comprise NAND memory, such may include nonvolatilememory comprising charge-trapping material.

The substrate 12 may be considered to comprise a front side surface 15and a back side surface 17 in opposing relation to the front sidesurface. In the shown embodiment, all of the integrated circuit levels14, 16, 18 and 20 are formed over the front side surface 15. In otherembodiments, some integrated circuitry may also be formed over the backside surface 17. However, the majority of the integrated circuitry willgenerally be over the front side surface 15.

An electrically conductive line 22 extends over the uppermost integratedcircuit level 20. The electrically conductive line 22 may comprise anysuitable composition or combination of compositions, and may, forexample, comprise, consist essentially of, or consist of copper oraluminum. The electrically conductive line 22 may correspond to a bondpad supporting layer. Accordingly, line 22 may be in electrical contactwith integrated circuitry of one or more of levels 14, 16, 18 and 20,and utilized for electrically connecting the integrated circuitry of oneor more of the levels to locations where bond pads are formed to connectwith circuitry external of that contained within semiconductorconstruction 10.

Line 22 may be an example of one of many bond pad supporting layersformed across semiconductor construction 10.

A thin layer 31 is shown extending across line 22. Such thin layer maycorrespond to a barrier layer utilized to block copper diffusion.Another copper-diffusion-blocking layer (not shown) may be under line 22in some embodiments. The barrier layer may be comprised of dielectricmaterial, such as, for example, nitrogen-doped silicon carbide.

A first passivation material 24 is formed over line 22, and a secondpassivation material 26 is formed over the first passivation material24. The first passivation material 24 may be a passivation oxide, andmay, for example, comprise, consist essentially of, or consist ofsilicon dioxide. The second passivation material 26 may be a passivationnitride; and may, for example, comprise, consist essentially of, orconsist of silicon nitride (for DRAM) or silicon oxynitride (for NAND).The first and second passivation materials may be formed utilizing anysuitable processing, including, for example, chemical vapor deposition(CVD).

In the shown embodiment, the first passivation material 24 is directlyagainst barrier layer 31 (in other words, touches the barrier layer);and the second passivation material 26 is directly against the firstpassivation material.

Construction 10 may be considered to have a front side and a back sideanalogous to the front and back sides of base 12. Specifically,construction 10 may be considered to have a front side 21 comprising asurface 27 of passivation material 26; and to have a back side 23comprising a surface 29 of base 12.

FIG. 2 shows a three-dimensional view of the construction 10 comprisingthe cross-section of FIG. 1. The various layers of FIG. 1 are not shownin FIG. 2 to simplify the drawing.

Referring to FIG. 3, insulative material 28 is deposited across thefront side 21 and back side 23 of construction 10. The insulativematerial 28 across the front side 21 may be referred to as a first layer30 of the insulative material, and the insulative material 28 along theback side 23 may be referred to as a second layer 32 of the insulativematerial.

The insulative material 28 may be formed by any suitable process, and inexample embodiments may be formed by atomic layer deposition. Theprocessing utilized to form material 28 deposits the material across allexposed surfaces of construction 10 (or at least all of the exposedsurfaces that are of appropriate composition), regardless of theorientation of the surfaces within a process chamber. Since material 28deposits simultaneously across the front side and back side of thewafer, the flipping of the semiconductor construction discussed above inthe “background” section of this disclosure may be avoided.Specifically, insulative material 28 can be deposited across back sidesurface 23 even when the back side surface faces downwardly in areaction chamber.

It may be desired to form material 28 at a processing temperature lowenough to avoid melting or otherwise adversely affecting compositionswithin the integrated circuit levels 14, 16, 18 and 20; and yet highenough to anneal, or otherwise thermally treat, one or both ofpassivation materials 24 and 26. For instance, it may be desired toavoid melting of materials (for example, aluminum) utilized in wiringand other integrated structures. In some embodiments, it may be desiredto form material 28 at a processing temperature of from greater than orequal to about 300° C. to less than or equal to about 500° C.; with anexample processing temperature being about 450° C.

The processing temperature utilized for deposition of material 28 may besuitable for desired thermal treatment of various passivation materials.For instance, the thermal treatment may anneal the materials to causehydrogen to migrate from passivation materials to transistors and otherstructures comprising semiconductor materials to terminate danglingbonds and thereby improve device performance. If the deposition ofmaterial 28 is at a sufficient temperature for desired thermal treatmentof passivation materials, such thermal treatment may occursimultaneously with the deposition of material 28.

In some embodiments, material 28 may comprise, consist essentially of,or consist of one or both of silicon nitride and silicon oxynitride; andmay be formed by PEALD. The PEALD may be conducted while maintainingconstruction 10 at a temperature of from about 300° C. to about 500° C.(with an example temperature being about 450° C.). The silicon nitride,or silicon oxynitride, may be deposited from any suitable precursors.Example precursors include dichlorosilane and ammonia. The precursorsmay be flowed into a reaction chamber utilizing any suitable carriergas, such as, for example, nitrogen.

An example apparatus which may be utilized for PEALD is shown in FIG. 8as apparatus 100. The apparatus comprises a furnace having a sidewall102 extending around a reaction chamber 104. The reaction chamber isconfigured for maintaining a plasma 106 therein.

Ports 108 and 110 extended through the sidewall, and are configured sothat reactant materials may be introduced into the chamber, and so thatreaction by-products may be flushed from the chamber. A valve 112 isdiagrammatically illustrated extending across port 108, and anothervalve 114 is diagrammatically illustrated extending across port 110. Inoperation, the valves may be utilized for controlling flow of reactants,reaction by-products, and purge gases into and out of the reactionchamber.

A substrate holder 116 is diagrammatically illustrated at the bottom ofthe chamber, and such is shown retaining a plurality of semiconductorconstructions 10, 10 a and 10 b within the chamber. The semiconductorconstructions may be identical to one another. Semiconductorconstruction 10 is shown to have a front side 21 and a back side 23, andis positioned so that the front side surface is facing upwardly.

The substrate holder 116 is configured to have a gap 118 beneath theback side of the substrate 10 so that a surface of the back side isexposed to ALD conditions within the chamber. Accordingly, material maybe simultaneously deposited across both the front side 21 and the backside 23 during ALD within the chamber. Similar gaps 117 and 119 arebeneath semiconductor constructions 10 a and 10 b, respectively.

Although the apparatus 100 is shown processing a batch of semiconductorconstructions, in other embodiments the apparatus may be configured toprocess a single semiconductor construction.

PEALD is an example method for forming material 28. Any method suitableto form material 28 simultaneously on both the front side and back sideof a wafer may be used. Other example methods are CVD andplasma-assisted CVD.

Referring again to FIG. 3, the insulative material 28 may be depositedto any suitable thickness. In some embodiments it may be desired to formmaterial 28 to be very thin to avoid having the material substantiallyalter conventional semiconductor processing, and to reduce costsassociated with the material. For instance, if material 28 consists ofsilicon nitride or silicon oxynitride, the material may be formed to athickness of less than or equal to about 80 nanometers, less than about15 nanometers, and in some embodiments may be formed to a thickness offrom about 10 nanometers to about 15 nanometers. In other embodiments,it may be desired to form material 28 to be thicker so that the layer isrobust when exposed to possible mechanical abrasion or other potentiallydamaging forces.

FIG. 10 shows an embodiment alternative to that of FIG. 3. Specifically,FIG. 10 shows an embodiment in which the insulative material 28 isformed to be between the materials 24 and 26, rather than over material26. Regardless, the material 28 of FIG. 10, like that of FIG. 3, issimultaneously formed across both the front and back sides of thesemiconductor construction.

Referring to FIG. 4, an insulative material 34 is formed over (and inthe shown embodiment, directly against) material 28 across the frontside 21 of semiconductor construction 10. Insulative material 34 maycomprise any suitable composition or combination of compositions; andmay, for example, comprise, consist essentially of, or consist ofphotosensitive polyimide. Material 34 may be formed to a thickness of atleast about 1000 nanometers. In some embodiments material 34 may bereplaced by conventional photoresist.

Material 34 may be formed by any suitable processing, including, forexample, spin-on processing and/or CVD. Material 34 may be formed whilethe front side 21 of construction 10 faces upwardly.

Referring to FIG. 5, material 34 is patterned to form a pair of openings38 and 40 extending therethrough. Such patterning may comprisingphotolithographic patterning of the photosensitive material 34.

Construction 10 is subsequently subjected to appropriate etchingconditions to extend openings 38 and 40 through materials 24, 26, 28, 31and 34. Accordingly, the openings are extended to expose an uppersurface of conductive material of line 22. Construction 10 may remain inan orientation with the front side 21 facing upwardly during the etchingutilized to extend openings 38 and 40 through materials 24, 26, 28, 31and 34. In some embodiments, the openings may penetrate partiallythrough line 22.

Referring to FIG. 6, conductive material 50 is formed within openings 38and 40. The conductive material may be formed by dipping construction 10within a plating bath, as is diagrammatically illustrated in FIG. 9.Material 34 is shown remaining over layer 28 during the filling ofopenings 38 and 40, as may be the case if material 34 is photosensitivepolyimide used to pattern DRAM cells. In other embodiments, material 34may be removed prior to filling the openings, as may be the case ifmaterial 34 is photoresist used to pattern NAND memory cells.

More specifically, FIG. 9 shows an apparatus 150 which comprises avessel 152 that retains a plating solution (or bath) 154. The platingsolution may be suitable for electroless plating of conductive material50 (FIG. 6), or for electrolytic plating of the material. In the shownembodiment, the apparatus is configured for electrolytic plating.Accordingly, an electrode 156 extends within bath 154 together withsemiconductor construction 10; and the electrode is electricallyconnected to the semiconductor construction 10 through a power source158. In operation, electrical power is provided by source 158 to drivetransfer of material from one or both of electrode 156 and bath 154 tosemiconductor construction 10 to form material 50 (FIG. 6) withinopenings 38 and 40 (FIG. 6).

If electroless plating is utilized instead of electrolytic plating, thepower source 158 and electrode 156 may be omitted, and instead materialmay electrolessly transfer from bath 154 onto a surface of line 22 togrow conductive material 50 (FIG. 6) within openings 38 and 40 (FIG. 6).In embodiments in which electroless plating is utilized, a surface ofconductive material of line 22 (FIG. 6) may be first activated toenhance growth of material 50 over such surface.

Referring again to FIG. 6, conductive material 50 may comprise anysuitable composition or combination of compositions. For instance,conductive material 50 may comprise one or more of nickel, palladium andgold. In some embodiments, material 50 may comprise a palladium/nickelalloy. Although material 50 is shown to be homogeneous, the material maycomprise multiple discrete layers formed by utilizing multiple separateplating steps. For instance, material 50 may comprise a layer of nickelhaving a layer of gold thereon.

Material 50 within openings 38 and 40 ultimately forms conductivecontact regions (i.e., bond pads) where electrical contact is formed tocircuitry external of construction 10. For instance, solder, wire bonds,etc., may be bonded to material 50; and may be in electrical connectionwith integrated circuitry of one or more of levels 14, 16, 18 and 20through conductive material 50 and electrically conductive line 22.

Material 50 is shown extending outwardly of openings 38 and 40, andlaterally beyond the openings to be across an upper surface of material34. In some embodiments, the plating may form material 50 to be entirelycontained within the openings, rather than extending outwardly of theopenings as shown in FIG. 6. If material 50 extends outwardly of theopenings, the material extending above layer 34 may be removed bychemical-mechanical polishing to form the structure shown in FIG. 7.

The insulative material 28 protects the backside 23 of semiconductorconstruction 10 from deposition of plated material 50 during the growthof material 50 within openings 38 and 40.

In some embodiments, the utilization of ALD (or other suitable methods)to form material 28 enables a layer of material to be extended acrossthe back side of the construction 10 without flipping the constructionduring formation of such layer. Such may avoid cracking and otherdefects which may be induced during prior art flipping of a wafer.Additionally, utilization of ALD (or other suitable methods) at anappropriate temperature to form material 28 may enable activation ofhydrogen of a passivation layer (or other advantages of suitable thermaltreatment and/or annealing of one or both of passivation layers 24 and26) to be conducted simultaneously with the deposition of material 28,which can consolidate processing steps relative to prior art procedureswhich formed a protective insulative layer along a back side of a waferin a separate process step from thermal treatment of one or morepassivation layers over the front side of the wafer.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

We claim:
 1. A semiconductor processing method, comprising: forming amonocrystalline silicon-containing semiconductor substrate to compriseone or more electrically conductive layers across a front side of thesubstrate, and to comprise one or more passivation layers over the oneor more electrically conductive layers; the semiconductor substratecomprising a back side in opposing relation to the front side; the backside having an exposed surface, and the front side having an exposedsurface comprising a surface of a passivation layer; utilizingplasma-enhanced atomic layer deposition to simultaneously deposit acomposition across the front side exposed surface and across the backside exposed surface; the composition on the front side exposed surfacebeing a first layer of the composition, and the composition across theback side exposed surface being a second layer of the composition;forming a layer of insulative material over the first layer of thecomposition; etching a pattern of openings extending through the layerof insulative material, through the first layer of the composition andthrough the one or more passivation layers to expose regions of the oneor more electrically conductive layers; and dipping the substrate in aplating bath to form conductive material within the openings.
 2. Themethod of claim 1 wherein the semiconductor substrate remains in anorientation with the front side facing up during the recited utilizationof the plasma-enhanced atomic layer deposition, and during the recitedformation of the layer of insulative material.
 3. The method of claim 1wherein the composition comprises one or both of silicon nitride andsilicon oxynitride.